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                            <div style="color:gray; word-break: break-all; font-size:12px;">原英文版地址: <a href="https://www.elastic.co/guide/en/elasticsearch/reference/7.7/analysis-keyword-tokenizer.html" rel="nofollow" target="_blank">https://www.elastic.co/guide/en/elasticsearch/reference/7.7/analysis-keyword-tokenizer.html</a>, 原文档版权归 www.elastic.co 所有<br/>本地英文版地址: <a href="../en/analysis-keyword-tokenizer.html" rel="nofollow" target="_blank">../en/analysis-keyword-tokenizer.html</a></div>
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<strong>重要</strong>: 此版本不会发布额外的bug修复或文档更新。最新信息请参考 <a href="https://www.elastic.co/guide/en/elasticsearch/reference/current/index.html" rel="nofollow">当前版本文档</a>。
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<span class="breadcrumb-node">Keyword Tokenizer</span>
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<h2 class="title">
<a id="analysis-keyword-tokenizer"></a>Keyword Tokenizer<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/analysis/tokenizers/keyword-tokenizer.asciidoc">edit</a>
</h2>
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<p>The <code class="literal">keyword</code> tokenizer  is a “noop” tokenizer that accepts whatever text it
is given and outputs the exact same text as a single term.  It can be combined
with token filters to normalise output, e.g. lower-casing email addresses.</p>
<h3>
<a id="_example_output_11"></a>Example output<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/analysis/tokenizers/keyword-tokenizer.asciidoc">edit</a>
</h3>
<div class="pre_wrapper lang-console">
<pre class="programlisting prettyprint lang-console">POST _analyze
{
  "tokenizer": "keyword",
  "text": "New York"
}</pre>
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<div class="console_widget" data-snippet="snippets/867.console"></div>
<p>The above sentence would produce the following term:</p>
<div class="pre_wrapper lang-text">
<pre class="programlisting prettyprint lang-text">[ New York ]</pre>
</div>
<h3>
<a id="analysis-keyword-tokenizer-token-filters"></a>Combine with token filters<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/analysis/tokenizers/keyword-tokenizer.asciidoc">edit</a>
</h3>
<p>You can combine the <code class="literal">keyword</code> tokenizer with token filters to normalise
structured data, such as product IDs or email addresses.</p>
<p>For example, the following <a class="xref" href="indices-analyze.html" title="Analyze API">analyze API</a> request uses the
<code class="literal">keyword</code> tokenizer and <a class="xref" href="analysis-lowercase-tokenfilter.html" title="Lowercase token filter"><code class="literal">lowercase</code></a> filter to
convert an email address to lowercase.</p>
<div class="pre_wrapper lang-console">
<pre class="programlisting prettyprint lang-console">POST _analyze
{
  "tokenizer": "keyword",
  "filter": [ "lowercase" ],
  "text": "john.SMITH@example.COM"
}</pre>
</div>
<div class="console_widget" data-snippet="snippets/868.console"></div>
<p>The request produces the following token:</p>
<div class="pre_wrapper lang-text">
<pre class="programlisting prettyprint lang-text">[ john.smith@example.com ]</pre>
</div>
<h3>
<a id="_configuration_12"></a>Configuration<a class="edit_me edit_me_private" rel="nofollow" title="Editing on GitHub is available to Elastic" href="https://github.com/elastic/elasticsearch/edit/7.7/docs/reference/analysis/tokenizers/keyword-tokenizer.asciidoc">edit</a>
</h3>
<p>The <code class="literal">keyword</code> tokenizer accepts the following parameters:</p>
<div class="informaltable">
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<p>
<code class="literal">buffer_size</code>
</p>
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<p>
The number of characters read into the term buffer in a single pass.
Defaults to <code class="literal">256</code>.  The term buffer will grow by this size until all the
text has been consumed.  It is advisable not to change this setting.
</p>
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